This invention relates to a sampling frequency converting apparatus for a digital television signal.
When a television signal is converted into a digital television signal, different sampling frequencies are often used in different television systems such as NTSC, PAL and SECAM systems, or in the same television system. If a plurality of digital units adopting respective different sampling frequencies are applied in a digital television signal transmission path, a sampling frequency converting apparatus is ncessary to convert a digital signal with one sampling frequency f.sub.A into a digital signal with another frequency f.sub.B. To perform such sampling frequency conversion in a purely digital manner, a frequency conversion method by means of a frequency of an integer multiplication of the sampling frequencies f.sub.A and f.sub.B has been proposed in the article "Sampling Rate Conversion for NTSC T.V." by B. G. Haskell, IEEE Communication Society, Mar. 3, 1977. However, this prior art method requires a high speed logic circuit (in comparison with the original sampling frequencies) and different circuit constructions for the conversions (f.sub.A .fwdarw.f.sub.B) and (f.sub.B .fwdarw.f.sub.A). Hence, this method is not advantageous in view of the complex circuit construction, the increased power consumption and the increased cost of production of the logic circuit.